1. Field of the Invention
The present invention relates to an electronic-component ("EC") supplying apparatus and method and in particular to the art of improving EC supplying efficiency.
2. Related Art Statement
Japanese Patent Application laid open for opposition under Publication No. 2(1990)-53954 discloses an EC supplying apparatus which supplies ECs to an EC mounting apparatus which mounts the ECs on an object such as a printed circuit board ("PCB"). The prior EC supplying apparatus includes two tables for supplying the ECs. Each of the two tables is supported by linear table guides provided on a bed, such that each table is movable relative to the bed. Each table supports a plurality of EC supplying cartridges such that respective component-supply portions of the cartridges are arranged along a straight line parallel to the table guides. A nut which is fixed to each table is threadedly engaged with a feeding screw which extends, on the bed, parallel to the table guides and which is rotated by a servomotor. Therefore, when each of the two servomotors is driven, the corresponding table is moved via the corresponding feeding screw and nut, so that the cartridges on that table are sequentially moved one by one to a component-supply position where each cartridge supplies ECs from the component-supply portion thereof.
Since the prior EC supplying apparatus includes not one but two tables, each table may have such dimensions which allow only one table to be used for supplying ECs to such a PCB which does not need more than the cartridges that can be supported by one table, and which require two tables to be used for supplying ECs to such a PCB which needs more than the cartridges that can be supported by one table but does not need more than the cartridges that can be supported by two tables. In the first case, the other table is not used or moved and, in the second case, the two tables may be moved, either alternately or simultaneously, for supplying ECs.
Thus, the tables employed in the above-indicated apparatus have smaller dimensions than those of conventional tables that had been designed to be suitable for such PCBs which need the largest number of cartridges, i.e., the largest number of ECs and/or the largest number of sorts of ECs. Accordingly, the tables of the prior EC supplying apparatus can respond more quickly and can move at higher speeds. Therefore, the EC supplying apparatus enjoys improved work efficiency. In addition, the vibration produced when each table is moved and stopped is reduced, which leads to reducing the possibility that the EC mounting apparatus fails to take (e.g., suck) ECs from the EC supplying apparatus.
However, the prior EC supplying apparatus employs at most two tables. Accordingly, if a greater number of cartridges are needed to supply ECs to a PCB, the two tables are required to have greater dimensions. In such cases, the tables cannot be moved at sufficiently high speeds, which leads to lowering the work efficiency of the EC supplying apparatus.
In the above-described situation, Japanese Patent Application laid open for inspection under Publication No. 6(1994)-342994 discloses an EC supplying apparatus which employs three or more tables for supplying ECs. In this apparatus, too, linear table guides are provided on a bed, and three or more tables are supported on the table guides such that each table is movable relative to the bed. Each table supports a plurality of EC supplying cartridges such that respective component-supply portions of the cartridges are arranged along a straight line parallel to the table guides. In addition, two carrier guides which extend parallel to the table guides are provided on the bed, and two carriers are supported on the carrier guides such that each carrier is movable relative to the bed. A nut which is fixed to each carrier is threadedly engaged with a feeding screw which extends, on the bed, parallel to the table guides and which is rotated by a servomotor. Each of the two carriers includes an engaging device which is disengageably engageable with one corresponding table, or each of two or more corresponding tables, and moves the one or each table to a component-supply area as an intermediate area on the bed in a direction parallel to the table guides, so that the one or each table supplies ECs in the component-supply area.
Since the above-indicated second prior apparatus employs two carriers, two tables of the three or more tables can simultaneously be moved by the two carriers, respectively. Thus, the second prior apparatus can advantageously supply ECs like the first prior apparatus wherein the two tables are directly driven and moved. In addition, each carrier can selectively be engaged with each of two or more tables. Therefore, the second prior apparatus can employ three or more tables for supplying ECs, even if it employs only two carriers. Accordingly, the tables employed in the second apparatus can have still smaller dimensions and can move at still higher speeds, which leads to further improving the work efficiency of the apparatus.
However, since the second prior apparatus has only two carriers, there are some cases where it may need much time to change a table which is currently supplying ECs in the component-supply area, to another table which is next to supply ECs in the same area. If, after one of the two carriers retracts, from the component-supply area, a first table which has completed the supplying of ECs, and before the same carrier engages a third table to follow a second table which is now supplying ECs in the component-supply area, and prepares for moving the third table to the component-supply area, the second table engaged with the other carrier completes the supplying of ECs, it needs a wasteful time after the second table completes the EC supplying and before the third table is ready for EC supplying.